1. Field of the Invention
The present invention relates to a semiconductor processing apparatus. In particular, it relates to a semiconductor processing apparatus that processes a semiconductor wafer while adjusting the temperature thereof.
2. Description of the Related Art
With the recent trend toward higher and higher packaging density of semiconductor devices, circuit patterns are becoming increasingly smaller, and dimension precision requirements are being increasingly severe. With this demand, temperature control of the wafer being processed has become very important. For example, in an etching process in which a high aspect ratio is required, in order to implement anisotropic etching, etching is performed while depositing an organic polymer on the side wall of the part being etched. However, deposition of the organic polymer covering the side wall is varied under the influence of temperature. That is, the temperature of the wafer being processed affects the etch rate or the resulting shape, and if the temperature distribution is non-uniform, the amount of deposited side wall protective film varies in the surface of the wafer. As a result, there arises a problem in that the resulting shape varies with location in the wafer surface, and the circuit patterns of semiconductor elements cut from the wafer and thus, the performances thereof vary among the elements.
In addition, in recent semiconductor manufacturing processes, wafers with larger diameters are handled, and the plasma, the applied power and the heat input from the apparatus to the wafer are increased. For example, in semiconductor manufacture involving a wafer having a diameter of 300 mm, a bias power in the order of 3 kW is applied to the wafer during the process of etching an interlayer insulating film formed on the wafer. In view of such a circumstance, in a semiconductor manufacturing apparatus, it is technically essential that the temperature of the semiconductor wafer is appropriately controlled in the surface of the wafer during the processing thereof.
In a conventional semiconductor manufacturing apparatus using a plasma, a wafer being plasma-processed is electrostatically stuck to and held on a stage (sample holder) by the action of electrostatic chuck provided on the stage. In addition, in order to assure adequate heat transfer between the wafer and the stage to adjust the temperature of the wafer, a heat conductive gas (typically, helium) is introduced to adjust the temperature of the wafer.
The range of the temperature of the wafer to be adjusted varies with the process. For example, the temperature of the stage that holds the wafer is required to be stably controlled over a wide range from a low temperature of −40° C. to a temperature on the order of 100° C. during the processing of the wafer. That is, it has become necessary that even if the wafer stage in the plasma processing apparatus is subjected to a significant heat input ranging widely from low temperature to high temperature, an uniform temperature distribution is provided in the surface of the wafer.
In addition, in recent years, demands for non-volatile memories including MRAM and Ferbam have been increased. To etch the materials of these memories, an extremely high temperature of 400° C. to 500° C. is required. In this case also, since redeposition of a reaction product affects the etching, it is required to properly control the wafer temperature.
As a technique for controlling the temperature of the wafer being processed, there is disclosed a technique in which first and second heat conductive gases are introduced between the wafer and a support for carrying the wafer, and the pressures of the first and second gases are controlled to adjust the heat conduction. In addition, this prior art discloses a technique in which, in order to process the wafer while keeping the temperature thereof constant in the above-described arrangement, an object to be processed for monitoring is used and the temperature distribution in the surface thereof is previously determined, and then, the amounts of the first and second heat conductive gases supplied and discharged via a first and second gas channels are set (for example, see Patent Reference 1).
[Patent Reference 1]
Japanese Patent Laid-Open No. 2002-305188